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Background: The concept of the use of MRI for image-guided adaptive brachytherapy (IGABT) in locally advanced cervical cancer was introduced 20 years ago. Here, we report on EMBRACE-I, which aimed to evaluate local tumour control and morbidity after chemoradiotherapy and MRI-based IGABT., Methods: EMBRACE-I was a prospective, observational, multicentre cohort study. Data from patients from 24 centres in Europe, Asia, and North America were prospectively collected. The inclusion criteria were patients older than 18 years, with biopsy-proven squamous cell carcinoma, adenocarcinoma, or adenosquamous carcinoma of the uterine cervix, The International Federation of Gynecology and Obstetrics (FIGO) stage IB-IVA disease or FIGO stage IVB disease restricted to paraaortic lymph metastasis below the L1-L2 interspace, suitable for curative treatment. Treatment consisted of chemoradiotherapy (weekly intravenous cisplatin 40 mg/m 2 , 5-6 cycles, 1 day per cycle, plus 45-50 Gy external-beam radiotherapy delivered in 1·8-2 Gy fractions) followed by MRI-based IGABT. The MRI-based IGABT target volume definition and dose reporting was according to Groupe Européen de Curiethérapie European Society for Radiation Oncology recommendations. IGABT dose prescription was open according to institutional practice. Local control and late morbidity were selected as primary endpoints in all patients available for analysis. The study was registered with ClinicalTrials.gov, NCT00920920., Findings: Patient accrual began on July 30, 2008, and closed on Dec 29, 2015. A total of 1416 patients were registered in the database. After exclusion for not meeting patient selection criteria before treatment, being registered but not entered in the database, meeting the exclusion criteria, and being falsely excluded, data from 1341 patients were available for analysis of disease and data from 1251 patients were available for assessment of morbidity outcome. MRI-based IGABT including dose optimisation was done in 1317 (98·2%) of 1341 patients. Median high-risk clinical target volume was 28 cm 3 (IQR 20-40) and median minimal dose to 90% of the clinical target volume (D 90% ) was 90 Gy (IQR 85-94) equi-effective dose in 2 Gy per fraction. At a median follow-up of 51 months (IQR 20-64), actuarial overall 5-year local control was 92% (95% CI 90-93). Actuarial cumulative 5-year incidence of grade 3-5 morbidity was 6·8% (95% CI 5·4-8·6) for genitourinary events, 8·5% (6·9-10·6) for gastrointestinal events, 5·7% (4·3-7·6) for vaginal events, and 3·2% (2·2-4·5) for fistulae., Interpretation: Chemoradiotherapy and MRI-based IGABT result in effective and stable long-term local control across all stages of locally advanced cervical cancer, with a limited severe morbidity per organ. These results represent a positive breakthrough in the treatment of locally advanced cervical cancer, which might be used as a benchmark for clinical practice and all future studies., Funding: Medical University of Vienna, Aarhus University Hospital, Elekta AB, and Varian Medical Systems., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Purpose: For patients with cervical cancer the delivery of chemotherapy with radiotherapy improves survival compared with radiotherapy alone. However, high rates of acute hematologic toxicity occur when combining both therapies due to the damage of the red bone marrow (RBM). This study aimed to reduce the radiation damage to the RBM. A tool has been developed for semi-automatic delineation of the red bone marrow based on MR-only. This delineation can be included into the treatment planning process to reduce the volume of RBM irradiated in patients receiving pelvic radiation therapy., Methods: 13 patients with cervical cancer were enrolled. All the patients underwent MR, CT and FDG-PET imaging. A tool for RBM determination from water and fat MR images was developed. Our MR-based RBM tool was optimized and validated with the FDG-PET scans of the patients., Results: Our tool identified RBM regions in the pelvic area. The mean total volume of these regions was 34% of the pelvic bone marrow. The corresponding SUV values based on the FDG-PET scans were above the reported threshold of active/red bone marrow., Conclusion: This study shows that delineations of the RBM for the radiotherapy with RBM sparing can be generated semi-automatically using MR scans only., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Purpose: Upfront quality assurance (QA) is considered essential when starting a multicenter clinical trial in radiotherapy. Despite the long experience gained for external beam radiotherapy (EBRT) trials, there are only limited audit QA methods for brachytherapy (BT) and none include the specific aspects of image guided adaptive brachytherapy (IGABT)., Methods and Materials: EMBRACE is a prospective multicenter trial aiming to assess the impact of (MRI)-based IGABT in locally advanced cervical cancer. An EMBRACE dummy run was designed to identify sources and magnitude of uncertainties and errors considered important for the evaluation of clinical, and dosimetric parameters and their relation to outcome. Contouring, treatment planning and dose reporting was evaluated and scored with a categorical scale of 1-10. Active feedback to centers was provided to improve protocol compliance and reporting. A second dummy run was required in case of major deviations (score <7) for any item., Results: Overall 27/30 centers passed the dummy run. 16 centers had to repeat the dummy run in order to clarify major inconsistencies to the protocol. The most pronounced variations were related to contouring for both EBRT and BT. Centers with experience in IGABT (>30 cases) had better performance as compared to centers with limited experience., Conclusion: The comprehensive dummy run designed for the EMBRACE trial has been a feasible tool for QA in IGABT of cervix cancer. It should be considered for future IGABT trials and could serve as the basis for continuous quality checks for brachytherapy centers., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Purpose: To study the impact of MRI-guided treatment planning on dose/volume parameters in pulsed dose rate (PDR) brachytherapy (BT) for cervical cancer. Additionally, we investigated the potential benefit of an intracavitary/interstitial (IC/IS) modification of the classical tandem ovoid applicator., Material and Methods: For 24 patients we compared Standard PDR BT plans, Scaled Standard plans and MRI-guided Optimised plans. The total EBRT/BT prescribed dose to Manchester point A or to 90% of the HR-CTV (D90 HR-CTV) expressed in EQD(2) was 80 Gy(alphabeta10) in 17 patients (Period I) and 84 Gy(alphabeta10) in 7 patients (Period II). The constraints to 2 cm(3) of the OAR were 90 Gy(alphabeta3) for bladder and 75 Gy(alphabeta3) for rectum, sigmoid and bowel. Most cases were treated with a traditional intracavitary tandem ovoid applicator. In 6 patients we used a newly designed combined IC/IS modification for the second PDR fraction and investigated the benefit of the interstitial part., Results: The average gain of MRI-guided optimisation expressed in D90 HR-CTV was 4+/-9 Gy(alphabeta10) (p<0.001) and 10+/-7 Gy(alphabeta10) (p=0.003) in the two periods. The dose to 2 cm(3) of the OAR met the constraints. In the group that was treated with the combined IC/IS approach, we could increase the D90 HR-CTV for the second PDR fraction with 5.4+/-4.2 Gy(alphabeta10) (p=0.005) and the D100 with 4.8+/-3.1 Gy(alphabeta10) (p=0.07)., Conclusions: Three-dimensional MRI-guided treatment planning and optimisation improves the DVH parameters compared to conventional planning strategies. Additional improvement can be achieved by using a combined IC/IS approach.

Purpose: To evaluate the methods of applicator reconstruction in 3D MR-based planning for brachytherapy of cervical cancer, and to investigate applicator shifts and changes in DVH parameters during PDR treatment., Methods: For each application MR scans with applicator in situ were made: three T2-weighted (4.5 mm slices) Turbo Spin Echo (TSE) scans and a balanced Steady State Free Precession scan (1.5 mm). Three observers tested two applicator reconstruction methods: (A) directly on the bSSFP scan and (B) on a resampled combination of the three T2-weighted scans. For 10 patients MR imaging was repeated on the second day of each PDR fraction to determine applicator shifts and changes in DVH parameters., Results: For both applicator reconstruction methods the interobserver variation for the DVH parameters was comparable (average <1.5% in dose). Differences between the two methods were larger (up to 6.4% for target) and were related to position differences during MR scanning. The average applicator shift relative to the pelvic structures was 5-6 mm into the ventral direction and 3-4 mm cranially. For a single PDR fraction, the average D90 (HR-CTV) on 'day 2' was 0.2 (SD 2.0) Gy lower than that for day 1. The average increase in D(2 cc) (bladder) was 1.0 (SD 3.0) Gy(alphabeta3) for a single PDR fraction. If the effect of both fractions was combined, for 1 patient a total decrease of D90 of 7 Gy(alphabeta10) was found, whereas for another patient the total increase in bladder dose was 12 Gy(alphabeta3)., Conclusions: Applicator reconstruction on MR data is feasible. In the overall accuracy during PDR brachytherapy the reconstruction uncertainty is of minor importance. Applicator and/or organ movement during the course of the PDR fraction produce larger uncertainties.

In this study, MR B(+)(1) imaging is employed to experimentally verify the validity of FDTD simulations of electromagnetic field patterns in human anatomies. Measurements and FDTD simulations of the B(+)(1) field induced by a 3 T MR body coil in a human corpse were performed. It was found that MR B(+)(1) imaging is a sensitive method to measure the radiofrequency (RF) magnetic field inside a human anatomy with a precision of approximately 3.5%. A good correlation was found between the B(+)(1) measurements and FDTD simulations. The measured B(+)(1) pattern for a human pelvis consisted of a global, diagonal modulation pattern plus local B(+)(1) heterogeneties. It is believed that these local B(+)(1) field variations are the result of peaks in the induced electric currents, which could not be resolved by the FDTD simulations on a 5 mm(3) simulation grid. The findings from this study demonstrate that B(+)(1) imaging is a valuable experimental technique to gain more knowledge about the dielectric interaction of RF fields with the human anatomy.

In this paper the concept of using B1+ imaging as a means to validate SAR models for radiofrequency hyperthermia is presented. As in radiofrequency hyperthermia, in common clinical MR imaging which applies RF frequencies between 64 and 128 MHz, the RF field distribution inside a patient is largely determined by the dielectric distribution of the anatomy. Modern MR imaging techniques allow measurement of the RF magnetic field component B1+ making it possible to measure at high resolution the dielectric interaction of the RF field with the patient. Given these considerations, we propose to use MR imaging to verify the validity of our dielectric patient model used for SAR models of radiofrequency hyperthermia. The aim of this study was to investigate the feasibility of this concept by performing B1+ measurements and simulations on cylindrical split phantoms consisting of materials with dielectric properties similar to human tissue types. Important topics of investigation were the accuracy and sensitivity of B1+ measurements and the validity of the electric model of the MR body coil. The measurements were performed on a clinical 1.5 T MR scanner with its quadrature body coil operating at 64 MHz. It was shown that even small B1+ variations of 2 to 5% could be measured reliably in the phantom experiments. An electrical model of the transmit coil was implemented on our FDTD-based hyperthermia treatment planning platform and the RF field distributions were calculated assuming an idealized quadrature current distribution in the coil. A quantitatively good correlation between measurements and simulations was found for phantoms consisting of water and oil, while highly conductive phantoms show considerable deviations. However, assuming linear excitation for these conductive phantoms resulted in good correspondence. As an explanation it is suggested that the coil is being detuned due to the inductive nature of the conductive phantoms, breaking up the phase difference of pi/2 between the two quadrature modes. It is concluded that B1+ imaging is an accurate and sensitive method for obtaining quantitative information about the RF field in phantoms. The electrical model of the body coil is inadequate for highly conductive phantoms. It is expected that for experiments on human bodies the inductive coupling is also significant, demonstrating the need for a full resonant FDTD model of the transmit coil. This will be pursued in the near future.

Dosimetric intra-fraction uncertainties in MRI-guided brachytherapy were analysed for HR-CTV and OARs. While dose differences were generally small, individual outliers occurred. In contrast to HDR, patients treated with PDR show increased mean rectal dose over time. Re-imaging prior to dose delivery helps to detect unfavorable anatomical changes, and allows for intervention. [ABSTRACT FROM AUTHOR]

Purpose: The goal of this study was to determine the dose contributions from image guided adaptive brachytherapy (IGABT) to individual suspicious pelvic lymph nodes (pLNN) in cervical cancer patients. Data were collected in two cancer centers, University of Pittsburgh Cancer Institute (UPCI) and University Medical Center Utrecht (UMCU). Material and methods: 27 and 15 patients with node positive cervical cancer treated with HDR (high dose rate) or PDR (pulsed dose rate)-IGABT were analyzed. HDR-IGABT (UPCI) was delivered with CT/MRI compatible tandem-ring applicators with 5.0-6.0 Gy x five fractions. PDR-IGABT (UMCU) dose was delivered with Utrecht tandem-ovoid applicators with 32 x 0.6 Gy x two fractions. Pelvic lymph nodes with short axis diameter of ≥ 5 mm on pre-treatment MRI or PET-CT were contoured for all BT-plans. Dose contributions to individual pLNN expressed as D90 (dose to 90% of the volume) were calculated from dose-volume histograms as absolute and relative physical dose (% of the reference dose) for each fraction. For each node, the total dose from all fractions was calculated, expressed in EQD2 (equivalent total dose in 2 Gy fractions). Results: Fifty-seven (UPCI) and 40 (UMCU) individual pLNN were contoured. The mean D90 pLNN was 10.8% (range 5.7-25.1%) and 20.5% (range 6.8-93.3%), respectively, and therefore different in the two centers. These values translate into 2.7 Gy (1.3-6.6 Gy) EQD2 and 7.1 Gy (2.2-36.7 Gy) EQD2, respectively. Differences are caused by the location of the individual nodes in relation to the spatial dose distribution of IGABT, differences in total dose administered and radiobiology (HDR versus PDR). Conclusions: The IGABT dose contribution to individual pelvic nodes depends on patient and treatment related factors, and varies considerably. [ABSTRACT FROM AUTHOR]

Abstract: Background and purpose: To compare MRI-guided treatment planning approaches between four centres that use tandem-ovoid applicators. Material and methods: Four centres generated three treatment plans for four patients: standard, optimised intracavitary, and optimised intracavitary/interstitial. Prescribed D90 High-Risk CTV (HR-CTV) was 85Gy EQD2 (external-beam radiotherapy and brachytherapy), while the D2cc OAR limit was 90Gy EQD2 for bladder and 75Gy EQD2 for rectum, sigmoid, and bowel, respectively. DVH-parameters, source loading patterns and spatial dose distributions of the three treatment plans were compared. Results: The standard plans of the different centres were comparable with respect to the D90 HR-CTV, but differed in OAR doses. MRI-guided intracavitary optimisation resulted in organ sparing and smaller variation in DVH parameters between the centres. Adding interstitial needles led to target dose escalation while respecting the OAR constraints. However, substantial differences in relative weights of the applicator parts resulted in an increased variation in DVH parameters and locations of high dose regions. Conclusions: MRI-guided brachytherapy treatment planning optimisation provides the possibility to increase the dose to the HR-CTV and spare the OARs. Depending on the degree of conformity the centres make different choices in relative weighting of applicator parts, leading to different dose distributions. [Copyright &y& Elsevier]

Abstract: Purpose: To evaluate dosimetric parameters and clinical outcome for cervical cancer patients treated with chemo-radiation and MR-image guided adaptive brachytherapy (MR-IGABT) using tandem-ovoid applicators for intracavitary or combined intracavitary/interstitial approaches. Method: This retrospective analysis includes 46 patients treated between 2006 and 2008. Dose–volume parameters D90 HR-CTV (high-risk clinical target volume) and D2cc OARs (organs at risk) were determined and converted into biologically equivalent doses in 2Gy fractions (EQD2). Clinical outcome parameters (local control (LC), progression free survival (PFS) and overall survival (OS)) were analysed actuarially and late morbidity crude rates were scored using CTCAEv3.0. Results: Mean D90 HR-CTV was 84 (SD9) Gy EQD2 for HR-CTV volumes of mean 57 (SD37) cm3 at time of first brachytherapy (BT). Median follow-up was 41 (range, 4–67)months. Three year LC, PFS, and OS rates were 93, 71, and 65%, respectively. Node negative patients had significantly higher 3-year survival rates compared to node positive ones (PFS 85 versus 53% (p =0.013), OS 77 versus 50% (p =0.032), respectively) with an even larger difference for patients with FIGO stages IB-IIB (PFS 87 versus 42% (p =0.002), OS 83 versus 46% (p =0.007), respectively). Late grade 3–4 mainly gastrointestinal or vaginal morbidity was observed in 4 patients (9.5%). No correlations were seen between morbidity and D2cc OAR values. Conclusion: (Chemo-) radiation and MR-IGABT with tandem-ovoid applicators result in high LC and promising survival rates with reasonable morbidity. [Copyright &y& Elsevier]

Abstract: Purpose: To compare two methods of DVH parameter determination for combined external beam and brachytherapy treatment of cervical cancer. Materials and methods: Clinical treatment plans from five patients were used in this study. We simulated two applications given with PDR (32×60cGy per application, given hourly) or HDR (4×7Gy in two applications; each application of two fractions of 7Gy, given within 17h) standard and optimised treatment plans, all combined with IMRT (25×1.8Gy). Additionally, we simulated an external beam (EBRT) boost to pathological lymph nodes or the parametrium (7×2Gy). We determined D90 of the high-risk CTV (HR-CTV) and D 2cc of bladder and rectum in EQD2 in two ways. (1) ‘Parameter adding’: assuming a uniform contribution of the EBRT dose distribution and adding the values of DVH parameters for the two brachytherapy insertions, and (2) ‘distributions adding’: summing 3D biological dose distributions of IMRT and brachytherapy plans and subsequently determining the values of the DVH parameters. We took α/β=10Gy for HR-CTV, α/β=3Gy otherwise and half-time of repair 1.5h. Results: Without EBRT boost, ‘parameter adding’ yielded a good approximation. With an EBRT boost to lymph nodes, the total D90 HR-CTV was underestimated by 2.6 (SD 1.3)% for PDR and 2.8 (SD 1.4)% for HDR. This was even worse with a parametrium boost: 9.1 (SD 6.2)% for PDR and 9.9 (SD 6.2)% for HDR. Conclusion: Without an EBRT boost ‘parameter adding’, as proposed by the GEC-ESTRO, yielded accurate results for the values for DVH parameters. If an EBRT boost is given ‘distributions adding’ should be considered. [Copyright &y& Elsevier]

Purpose: The aim of this study was to investigate the influence of brachytherapy technique and applicator type on target dose, isodose surface volumes, and organ-at-risk (OAR) dose.Methods and Materials: Nine hundred two patients treated with tandem/ovoids (T&O) (n = 299) and tandem/ring (T&R) (n = 603) applicators from 16 EMBRACE centers were analyzed. Patients received external beam radiation therapy and magnetic resonance imaging guided brachytherapy with dose prescription according to departmental practice. Centers were divided into 4 groups, according to applicator/technique: Ovoids and ring centers treating mainly with the intracavitary (IC) technique and ovoids and ring centers treating routinely with the intracavitary/interstitial (IC/IS) technique. V85Gy EQD210, CTVHR D90% (EQD210), and bladder, rectum, sigmoid, and vaginal 5-mm lateral-point doses (EQD23) were evaluated among center groups. Differences between T&O and T&R were tested with multivariable analysis.Results: For similar point A doses, mean CTVHR D90% was 3.3 Gy higher and V85Gy was 23% lower for ring-IC compared with ovoids-IC centers (at median target volumes). Mean bladder/rectum doses (D2cm3 and ICRU-point) were 3.2 to 7.7 Gy smaller and vaginal 5-mm lateral-point was 19.6 Gy higher for ring-IC centers. Routine use of IC/IS technique resulted in increased target dose, whereas V85Gy was stable (T&R) or decreased (T&O); reduced bladder and rectum D2cm3 and bladder ICRU-point by 3.5 to 5.0 Gy for ovoids centers; and similar OAR doses for ring centers. CTVHR D90% was 2.8 Gy higher, bladder D2cm3 4.3 Gy lower, rectovaginal ICRU-point 4.8 Gy lower, and vagina 5-mm lateral-point 22.4 Gy higher for ring-IC/IS versus ovoids-IC/IS centers. The P values were <.002 for all comparisons. Equivalently, significant differences were derived from the multivariable analysis.Conclusions: T&R-IC applicators have better target dose and dose conformity than T&O-IC in this representative patient cohort. IC applicators fail to cover large target volumes, whereas routine application of IC/IS improves target and OAR dose considerably. Patients treated with T&R show a more favorable therapeutic ratio when evaluating target, bladder/rectum doses, and V85Gy. A comprehensive view on technique/applicators should furthermore include practical considerations and clinical outcome. [ABSTRACT FROM AUTHOR]

Purpose Vaginal stenosis is a major problem following radiotherapy in cervical cancer. We investigated a new dose planning strategy for vaginal dose de-escalation (VDD). Materials and methods Fifty consecutive locally advanced cervical cancer patients without lower or middle vaginal involvement at diagnosis from 3 institutions were analysed. External beam radiotherapy was combined with MRI-guided brachytherapy. VDD was obtained by decreasing dwell times in ovoid/ring and increasing dwell times in tandem/needles. The aim was to maintain the target dose (D90 of HR-CTV ⩾ 85 Gy EQD2) while reducing the dose to the surface of the vagina to <140% of the physical fractional brachytherapy dose corresponding to a total EQD2 of 85 Gy. Results The mean vaginal loading (ovoid/ring) was reduced from 51% to 33% of the total loading with VDD, which significantly reduced the dose to the vaginal dose points ( p < 0.001) without compromising the target dose. The dose to the ICRU recto-vaginal point was reduced by a mean of 4 ± 4 Gy EQD2 ( p < 0.001), while doses to bladder and rectum (D 2cm 3 ) were reduced by 2 ± 2 Gy and 3 ± 2 Gy, respectively ( p < 0.001). Conclusions VDD significantly reduces dose to the upper vagina which is expected to result in reduction of vaginal stenosis. [ABSTRACT FROM AUTHOR]

Purpose: A simple scoring system (T-score, TS) for integrating findings from clinical examination and magnetic resonance imaging (MRI) of the primary tumor at diagnosis has shown strong prognostic capability for predicting local control and survival in locally advanced cervical cancer treated with chemoradiation and MRI-guided brachytherapy (BT). The aim was to validate the performance of TS using the multicenter EMBRACE I study and to evaluate the prognostic implications of TS regression obtained during initial chemoradiation.Methods and Materials: EMBRACE I recruited 1416 patients, of whom 1318 were available for TS. Patients were treated with chemoradiation followed by MRI-guided BT. A ranked ordinal scale of 0 to 3 points was used to assess 8 anatomic locations typical for local invasion of cervical cancer. TS was calculated separately at diagnosis (TSD) and at BT (TSBT) by the sum of points obtained from the 8 locations at the 2 occasions.Results: Median TSD and TSBT was 5 and 4, respectively. TS regression was observed in 71% and was an explanatory variable for BT technique (intracavitary vs intracavitary/interstitial) and major dose-volume histogram parameters for BT, such as high-risk clinical target (CTVHR), CTVHR D90 (minimal dose to 90% of the target volume), D2cm3 bladder (minimal dose to the most exposed 2 cm3 of the bladder), and D2cm3 rectum. TS regression (TSBT≤5) was associated with improved local control and survival and with less morbidity compared with patients with TSBT remaining high (>5) despite initial chemoradiation. TS regression was significant in multivariate analysis for both local control and survival when analyzed in consort with already established prognostic parameters related to the patient, disease, and treatment.Conclusions: TS was validated in a multicenter setting and proven to be a strong multidisciplinary platform for integration of clinical findings and imaging with the ability to quantitate local tumor regression and its prognostic implications regarding BT technique, dose-volume histogram parameters, local control, survival, and morbidity. [ABSTRACT FROM AUTHOR]

Purpose To demonstrate that V 60 Gy, V 75 Gy, and V 85 Gy isodose surface volumes can be accurately estimated from total reference air kerma (TRAK) in cervix cancer MRI-guided brachytherapy (BT). Methods and Materials 60 Gy, 75 Gy, and 85 Gy isodose surface volumes levels were obtained from treatment planning systems (V TPS ) for 239 EMBRACE study patients from five institutions treated with various dose rates, fractionation schedules and applicators. An equation for estimating V TPS from TRAK was derived. Furthermore, a surrogate Point A dose (Point A*) was proposed and tested for correlation with V 75 Gy. Results Predicted volumes V pred = 4965 (TRAK/dref) 3/2 + 170 (TRAK/dref) − 1.5 gave the best fit to V TPS . The difference between V TPS and predicted volumes was 0.0% ± 2.3%. All volumes were predicted within 10%. The prediction was valid for ( 1 ) high-dose rate and pulsed dose rate, ( 2 ) intracavitary vs. intracavitary/interstitial applicators, and ( 3 ) tandem-ring, tandem-ovoid, and mold. Point A* = 14 TRAK was converted to total EQD 2 and showed high correlation with V 75 Gy. Conclusions TRAK derived Isodose surface volumes may become a tool for assessment of treatment intensity. Furthermore, surrogate Point A ∗ doses can be applied for both intracavitary and intracavitary/interstitial BT and can be used to compare treatments across fractionation schedules. [ABSTRACT FROM AUTHOR]